diff --git a/.changeset/cold-session-batch-archive.md b/.changeset/cold-session-batch-archive.md
new file mode 100644
index 000000000..de17db9e5
--- /dev/null
+++ b/.changeset/cold-session-batch-archive.md
@@ -0,0 +1,5 @@
+---
+"@moonshot-ai/agent-core-v2": patch
+---
+
+Add a cold-session archive/restore path that patches the persisted metadata document, mirrors the flipped summary into the session-index read model, and republishes the archived bus event without materializing the session, backing the new `POST /api/v2/sessions:archive` / `:restore` batch endpoints (per-item results; live sessions still run the full lifecycle).
diff --git a/packages/agent-core-v2/src/index.ts b/packages/agent-core-v2/src/index.ts
index 487e1c4fd..472a56fb3 100644
--- a/packages/agent-core-v2/src/index.ts
+++ b/packages/agent-core-v2/src/index.ts
@@ -416,6 +416,7 @@ export * from '#/app/workspaceLifecycle/sessionLookup';
 export * from '#/workspace/workspaceContext/workspaceContext';
 export * from '#/workspace/sessionLifecycle/sessionLifecycle';
 export * from '#/workspace/sessionLifecycle/sessionLifecycleService';
+export * from '#/workspace/sessionLifecycle/coldSessionArchive';
 export * from '#/workspace/sessionLifecycle/internal/addressing';
 export * from '#/session/externalHooks/externalHooks';
 export * from '#/session/externalHooks/externalHooksService';
diff --git a/packages/agent-core-v2/src/workspace/sessionLifecycle/coldSessionArchive.ts b/packages/agent-core-v2/src/workspace/sessionLifecycle/coldSessionArchive.ts
new file mode 100644
index 000000000..1b031b3a5
--- /dev/null
+++ b/packages/agent-core-v2/src/workspace/sessionLifecycle/coldSessionArchive.ts
@@ -0,0 +1,67 @@
+/**
+ * `sessionLifecycle` domain — cold-session archive/restore without session
+ * materialization.
+ *
+ * Writes the archived flag straight into the persisted metadata document
+ * (`state.json` under the handler-chain scope derived through
+ * `internal/addressing` from the `bootstrap` sessions scope) via the
+ * `storage` access-pattern store, mirrors the flipped summary into the
+ * `sessionIndex` mirror queue (drained by the caller, never per item), and
+ * publishes the same `event.session.archived` bus event the live
+ * `ISessionLifecycleService.archive` emits through `event` — restore
+ * publishes nothing, matching the live `restore` (which only flips the
+ * flag through `ISessionMetadata`). `updatedAt` is preserved verbatim,
+ * mirroring `setArchived`'s `touchUpdatedAt: false` semantics, and every
+ * other persisted field survives the read-modify-write untouched. Call
+ * only for a session with no live handle in any workspace handler — a
+ * live session must go through the full lifecycle so its agents drain
+ * and its scope tears down; the direct write deliberately races a
+ * concurrent resume unsynchronized (the read model heals by
+ * reconciliation). Existence reads from `ISessionIndex`: an unknown id
+ * and an index entry whose document is unreadable both report
+ * `not_found`.
+ */
+
+import type { ServicesAccessor } from '#/_base/di/instantiation';
+import { IBootstrapService } from '#/app/bootstrap/bootstrap';
+import { IEventService } from '#/app/event/event';
+import { ISessionIndex, ISessionIndexMirror } from '#/app/sessionIndex/sessionIndex';
+import { IAtomicDocumentStore } from '#/persistence/interface/atomicDocumentStore';
+import type { SessionMeta } from '#/session/sessionMetadata/sessionMetadata';
+
+import { sessionScopeOf, workspacePersistenceScope } from './internal/addressing';
+
+export type ColdSessionArchiveOutcome = 'updated' | 'not_found';
+
+export async function setColdSessionArchived(
+  accessor: ServicesAccessor,
+  sessionId: string,
+  archived: boolean,
+): Promise<ColdSessionArchiveOutcome> {
+  const summary = await accessor.get(ISessionIndex).get(sessionId);
+  if (summary === undefined) return 'not_found';
+  const docs = accessor.get(IAtomicDocumentStore);
+  const metaScope = sessionScopeOf(
+    workspacePersistenceScope(
+      accessor.get(IBootstrapService).scope('sessions'),
+      summary.workspaceId,
+    ),
+    sessionId,
+  );
+  let persisted: SessionMeta | undefined;
+  try {
+    persisted = await docs.get<SessionMeta>(metaScope, 'state.json');
+  } catch {
+    persisted = undefined;
+  }
+  if (persisted === undefined) return 'not_found';
+  const archivedAt = archived ? Date.now() : undefined;
+  await docs.set(metaScope, 'state.json', { ...persisted, archived, archivedAt });
+  accessor.get(ISessionIndexMirror).record({ ...summary, archived, archivedAt });
+  if (archived) {
+    accessor
+      .get(IEventService)
+      .publish({ type: 'event.session.archived', payload: { sessionId } });
+  }
+  return 'updated';
+}
diff --git a/packages/kap-server/src/routes/v2/sessions.ts b/packages/kap-server/src/routes/v2/sessions.ts
index 4517e771e..f5d8df9c2 100644
--- a/packages/kap-server/src/routes/v2/sessions.ts
+++ b/packages/kap-server/src/routes/v2/sessions.ts
@@ -36,14 +36,35 @@
  * same edge pattern as v1's unpaged `GET /api/v1/sessions`. All sorts
  * share one comparator + one cursor encoding, so every sort paginates
  * identically.
+ *
+ * Batch actions: `POST /sessions:archive` / `POST /sessions:restore`
+ * (registered as `/sessions::{action}` — find-my-way splits a segment at
+ * its first `:`, so the wire path carries a single colon, same as the v1
+ * `/fs::browse` precedent) take `{ ids }` (non-empty, ≤5000 unique) and
+ * answer per-item results — `data.results[]` in input order with
+ * `ok` / `error`, plus `succeeded` / `failed` counts; only a body
+ * validation failure fails the whole request. A live session goes
+ * through the full `ISessionLifecycleService` chain (agents drain, scope
+ * teardown, mirror drain); a cold session is never materialized — its
+ * archived flag is patched straight into the persisted metadata
+ * document, mirrored into the read model, and (`:archive` only)
+ * announced through the same `event.session.archived` bus event the live
+ * lifecycle publishes, while `:restore` publishes nothing, matching the
+ * live restore. An unknown id folds into its own item as 40401. The
+ * batch ends with one shared `ISessionIndexMirror.drain()`, never one
+ * per item.
  */
 
 import { createHash } from 'node:crypto';
 
 import {
   ISessionIndex,
+  ISessionIndexMirror,
+  ISessionLifecycleService,
   IWorkspaceAliases,
   IWorkspaceService,
+  liveHandlerForSession,
+  setColdSessionArchived,
   type Scope,
   type SessionSummary,
 } from '@moonshot-ai/agent-core-v2';
@@ -64,6 +85,14 @@ interface V2SessionsRouteHost {
       reply: { send(payload: unknown): unknown },
     ) => Promise<void> | void,
   ): unknown;
+  post(
+    path: string,
+    options: { preHandler: unknown[]; schema?: Record<string, unknown> },
+    handler: (
+      req: { id: string; body: unknown; params: unknown; headers: Record<string, unknown> },
+      reply: { send(payload: unknown): unknown },
+    ) => Promise<void> | void,
+  ): unknown;
 }
 
 // ---------------------------------------------------------------------------
@@ -199,6 +228,43 @@ const v2SessionPageSchema = z.object({
 /** `40001 validation.failed` carries the offending fields (REST.md §1.4). */
 const detailsSchema = z.array(z.object({ path: z.string(), message: z.string() }));
 
+// ---------------------------------------------------------------------------
+// Batch archive / restore contract
+// ---------------------------------------------------------------------------
+
+/** Cap on unique ids per batch, keeping one request's edge work bounded. */
+const BATCH_IDS_MAX = 5000;
+
+/** Hot-path lifecycle calls run with this many in flight at most. */
+const BATCH_CONCURRENCY = 8;
+
+const v2SessionsBatchBodySchema = z
+  .object({ ids: z.array(z.string().min(1)).min(1) })
+  .superRefine((value, ctx) => {
+    if (new Set(value.ids).size > BATCH_IDS_MAX) {
+      ctx.addIssue({
+        code: 'custom',
+        message: `ids must contain at most ${BATCH_IDS_MAX} unique entries`,
+        path: ['ids'],
+        params: { code: ErrorCode.VALIDATION_FAILED },
+      });
+    }
+  });
+
+const v2SessionsBatchResultSchema = z.object({
+  results: z.array(
+    z.object({
+      id: z.string(),
+      ok: z.boolean(),
+      error: z.object({ code: z.number().int(), message: z.string() }).optional(),
+    }),
+  ),
+  succeeded: z.number().int(),
+  failed: z.number().int(),
+});
+
+type V2BatchItemResult = z.infer<typeof v2SessionsBatchResultSchema>['results'][number];
+
 type V2GitDomain = z.infer<typeof v2GitDomainSchema>;
 type V2SessionWire = z.infer<typeof v2SessionSchema>;
 
@@ -376,6 +442,77 @@ class GitDomainResolver {
 // Route
 // ---------------------------------------------------------------------------
 
+/**
+ * Run one `:archive` / `:restore` batch: live sessions through the full
+ * `ISessionLifecycleService` chain, cold sessions through the direct cold
+ * patch (no materialization); per-item failures fold into the result list
+ * in input order. Ends with a single shared mirror drain.
+ */
+async function runBatchArchive(
+  core: Scope,
+  action: 'archive' | 'restore',
+  rawIds: readonly string[],
+  requestId: string,
+  reply: { send(payload: unknown): unknown },
+): Promise<void> {
+  const archived = action === 'archive';
+  const ids = [...new Set(rawIds)];
+  const results: (V2BatchItemResult | undefined)[] = ids.map(() => undefined);
+
+  // Per-item work never throws: a failure folds into its own result and
+  // the rest of the batch still runs.
+  const applyOne = async (id: string): Promise<V2BatchItemResult> => {
+    try {
+      const liveHandler = liveHandlerForSession(core.accessor, id);
+      if (liveHandler !== undefined) {
+        const lifecycle = liveHandler.accessor.get(ISessionLifecycleService);
+        if (archived) await lifecycle.archive(id);
+        else await lifecycle.restore(id);
+        return { id, ok: true };
+      }
+      const outcome = await setColdSessionArchived(core.accessor, id, archived);
+      return outcome === 'updated'
+        ? { id, ok: true }
+        : {
+            id,
+            ok: false,
+            error: {
+              code: ErrorCode.SESSION_NOT_FOUND,
+              message: `session ${id} does not exist`,
+            },
+          };
+    } catch (error) {
+      return {
+        id,
+        ok: false,
+        error: {
+          code: ErrorCode.INTERNAL_ERROR,
+          message: error instanceof Error ? error.message : String(error),
+        },
+      };
+    }
+  };
+
+  let next = 0;
+  const workers = Array.from({ length: Math.min(BATCH_CONCURRENCY, ids.length) }, async () => {
+    while (next < ids.length) {
+      const index = next++;
+      results[index] = await applyOne(ids[index] as string);
+    }
+  });
+  await Promise.all(workers);
+  // One drain for the whole batch — cold records queue in the mirror, and
+  // the hot path already drained itself per call.
+  await core.accessor.get(ISessionIndexMirror).drain();
+
+  // Every slot was assigned by the workers — no undefined entries remain.
+  const settled = results as V2BatchItemResult[];
+  const succeeded = settled.filter((result) => result.ok).length;
+  reply.send(
+    okEnvelope({ results: settled, succeeded, failed: settled.length - succeeded }, requestId),
+  );
+}
+
 export function registerV2SessionsRoutes(app: V2SessionsRouteHost, core: Scope): void {
   const gitResolver = new GitDomainResolver(core);
 
@@ -551,4 +688,30 @@ export function registerV2SessionsRoutes(app: V2SessionsRouteHost, core: Scope):
     listRoute.options,
     listRoute.handler as Parameters<V2SessionsRouteHost['get']>[2],
   );
+
+  for (const action of ['archive', 'restore'] as const) {
+    const batchRoute = defineRoute(
+      {
+        method: 'POST',
+        // `/sessions::${action}` in find-my-way serves the wire path
+        // `/sessions:archive` / `/sessions:restore` (single colon).
+        path: `/sessions::${action}`,
+        body: v2SessionsBatchBodySchema,
+        success: { data: v2SessionsBatchResultSchema },
+        errors: {
+          [ErrorCode.VALIDATION_FAILED]: { detailsSchema },
+        },
+        description: `Batch-${action} sessions by id ({ ids }, ≤5000 unique). Per-item results — a missing session folds into its own item; cold sessions are patched without materialization.`,
+        tags: ['v2-sessions'],
+      },
+      async (req, reply) => {
+        await runBatchArchive(core, action, req.body.ids, req.id, reply);
+      },
+    );
+    app.post(
+      batchRoute.path,
+      batchRoute.options,
+      batchRoute.handler as Parameters<V2SessionsRouteHost['post']>[2],
+    );
+  }
 }
diff --git a/packages/kap-server/test/__snapshots__/apiSurface.snapshot.test.ts.snap b/packages/kap-server/test/__snapshots__/apiSurface.snapshot.test.ts.snap
index a12395892..fa51b2fdc 100644
--- a/packages/kap-server/test/__snapshots__/apiSurface.snapshot.test.ts.snap
+++ b/packages/kap-server/test/__snapshots__/apiSurface.snapshot.test.ts.snap
@@ -444,6 +444,14 @@ exports[`API surface snapshot > matches the documented v2 route table and meta e
       "POST",
       "/api/v1/workspaces/{workspace_id}/untrust",
     ],
+    [
+      "POST",
+      "/api/v2/sessions:archive",
+    ],
+    [
+      "POST",
+      "/api/v2/sessions:restore",
+    ],
     [
       "PUT",
       "/api/v1/providers/{provider_id}",
diff --git a/packages/kap-server/test/v2Sessions.test.ts b/packages/kap-server/test/v2Sessions.test.ts
index 3921c90fb..5a5b6fa65 100644
--- a/packages/kap-server/test/v2Sessions.test.ts
+++ b/packages/kap-server/test/v2Sessions.test.ts
@@ -1,13 +1,16 @@
 /**
- * Scenario: `/api/v2/sessions` domain-grouped session list query.
+ * Scenario: `/api/v2/sessions` domain-grouped session list query + batch actions.
  * Responsibilities: envelope wire shape (business outcome in `code`: 40001
  * invalid params / 40922 page_token mismatch), filters, sort orders, opaque
- * page tokens, git domain dedup/cache/degradation, v2 auth error shape, and
- * the activity-status mapper.
- * Wiring: real kap-server; `ISessionIndex` / `IGitService` stubbed via DI seeds.
+ * page tokens, page-number mode + total, git domain dedup/cache/degradation,
+ * v2 auth error shape, the activity-status mapper, and the
+ * `POST /sessions:archive` / `:restore` batch endpoints (per-item results,
+ * live/cold split, cold path never materializes).
+ * Wiring: real kap-server; the list tests stub `ISessionIndex` / `IGitService`
+ * via DI seeds, the batch tests run real sessions in a temp home.
  * Run: `pnpm --filter @moonshot-ai/kap-server exec vitest run test/v2Sessions.test.ts`.
  */
-import { mkdtemp, rm } from 'node:fs/promises';
+import { mkdtemp, readFile, rm } from 'node:fs/promises';
 import { tmpdir } from 'node:os';
 import { join } from 'node:path';
 
@@ -15,6 +18,15 @@ import {
   Error2,
   ErrorCodes,
   ISessionIndex,
+  ISessionLifecycleService,
+  IEventService,
+  IWorkspaceLifecycleService,
+  closeSessionById,
+  getLiveSessionById,
+  liveHandlerForSession,
+  resumeSessionById,
+  sessionDirOf,
+  type GlobalEvent,
   type SessionSummary,
 } from '@moonshot-ai/agent-core-v2';
 import {
@@ -22,7 +34,7 @@ import {
   type FsPullRequest,
   IGitService,
 } from '@moonshot-ai/agent-core-v2/app/git/git';
-import { afterEach, beforeEach, describe, expect, it } from 'vitest';
+import { afterEach, beforeEach, describe, expect, it, vi } from 'vitest';
 
 import { type RunningServer, startServer } from '../src/start';
 import { mapActivityStatus } from '../src/routes/v2/sessions';
@@ -492,6 +504,280 @@ describe('server /api/v2/sessions', () => {
   });
 });
 
+describe('server /api/v2/sessions batch archive/restore', () => {
+  interface BatchItemWire {
+    id: string;
+    ok: boolean;
+    error?: { code: number; message: string };
+  }
+
+  interface BatchWire {
+    results: BatchItemWire[];
+    succeeded: number;
+    failed: number;
+  }
+
+  interface BatchEnvelopeWire {
+    code: number;
+    msg: string;
+    data: BatchWire | null;
+    request_id: string;
+    details?: { path: string; message: string }[];
+  }
+
+  let server: RunningServer | undefined;
+  let home: string | undefined;
+  let base: string;
+
+  beforeEach(async () => {
+    home = await mkdtemp(join(tmpdir(), 'kimi-server-v2-sessions-batch-'));
+    server = await startServer({
+      hostIdentity: TEST_HOST_IDENTITY,
+      host: '127.0.0.1',
+      port: 0,
+      homeDir: home,
+      logLevel: 'silent',
+    });
+    base = `http://127.0.0.1:${server.port}`;
+  });
+
+  afterEach(async () => {
+    vi.restoreAllMocks();
+    if (server !== undefined) {
+      await server.close();
+      server = undefined;
+    }
+    if (home !== undefined) {
+      await new Promise((resolve) => setTimeout(resolve, 25));
+      await rm(home, { recursive: true, force: true, maxRetries: 5, retryDelay: 50 } as never);
+      home = undefined;
+    }
+  });
+
+  function core(): RunningServer['core']['accessor'] {
+    return (server as RunningServer).core.accessor;
+  }
+
+  /** Subscribe a bus-event collector; caller disposes the returned sub. */
+  function collectEvents(): { events: GlobalEvent[]; dispose(): void } {
+    const events: GlobalEvent[] = [];
+    const sub = core().get(IEventService).subscribe((event) => events.push(event));
+    return {
+      events,
+      dispose: () => {
+        sub.dispose();
+      },
+    };
+  }
+
+  async function createSession(): Promise<{ id: string; workspace_id: string }> {
+    const res = await authedFetch(server as RunningServer, base, '/api/v1/sessions', {
+      method: 'POST',
+      headers: { 'content-type': 'application/json' },
+      body: JSON.stringify({ metadata: { cwd: home } }),
+    });
+    const body = (await res.json()) as {
+      code: number;
+      data: { id: string; workspace_id: string };
+    };
+    expect(body.code).toBe(0);
+    return body.data;
+  }
+
+  async function postBatch(path: string, body?: unknown): Promise<BatchEnvelopeWire> {
+    const res = await authedFetch(server as RunningServer, base, path, {
+      method: 'POST',
+      headers: body !== undefined ? { 'content-type': 'application/json' } : {},
+      body: body !== undefined ? JSON.stringify(body) : undefined,
+    });
+    expect(res.status).toBe(200);
+    return (await res.json()) as BatchEnvelopeWire;
+  }
+
+  async function readStateJson(workspaceId: string, id: string): Promise<Record<string, unknown>> {
+    const dir = sessionDirOf(home as string, `sessions/${workspaceId}`, id);
+    return JSON.parse(await readFile(join(dir, 'state.json'), 'utf-8')) as Record<string, unknown>;
+  }
+
+  async function indexArchived(id: string): Promise<boolean | undefined> {
+    return (await core().get(ISessionIndex).get(id))?.archived;
+  }
+
+  async function listedIds(query = ''): Promise<string[]> {
+    const res = await authedFetch(server as RunningServer, base, `/api/v2/sessions${query}`);
+    const body = (await res.json()) as { code: number; data: { items: { id: string }[] } };
+    expect(body.code).toBe(0);
+    return body.data.items.map((item) => item.id);
+  }
+
+  it('archives a cold session without materializing it or touching a workspace handler', async () => {
+    const created = await createSession();
+    await closeSessionById(core(), created.id);
+    expect(getLiveSessionById(core(), created.id)).toBeUndefined();
+
+    // Any materialization (resume, or the v1 single-archive route) must go
+    // through handlerFor; the cold path never touches it.
+    const handlerForSpy = vi.spyOn(core().get(IWorkspaceLifecycleService), 'handlerFor');
+    const { events, dispose } = collectEvents();
+    const before = await readStateJson(created.workspace_id, created.id);
+
+    const body = await postBatch('/api/v2/sessions:archive', { ids: [created.id] });
+    expect(body.code).toBe(0);
+    expect(body.data).toMatchObject({
+      succeeded: 1,
+      failed: 0,
+      results: [{ id: created.id, ok: true }],
+    });
+
+    expect(handlerForSpy).not.toHaveBeenCalled();
+    expect(getLiveSessionById(core(), created.id)).toBeUndefined();
+
+    // The persisted metadata flips exactly like setArchived(true): archived
+    // (+ archivedAt), updatedAt and every other field preserved.
+    const after = await readStateJson(created.workspace_id, created.id);
+    expect(after['archived']).toBe(true);
+    expect(typeof after['archivedAt']).toBe('number');
+    expect(after['updatedAt']).toBe(before['updatedAt']);
+    expect(after['createdAt']).toBe(before['createdAt']);
+    expect(after['agents']).toEqual(before['agents']);
+
+    // The route drained the mirror once: the read model already answers
+    // archived, and the v2 list serves the session under meta.archived=true.
+    expect(await indexArchived(created.id)).toBe(true);
+    expect(await listedIds('?meta.archived=true')).toEqual([created.id]);
+    expect(await listedIds()).toEqual([]);
+
+    // Same bus event the live lifecycle publishes.
+    expect(events.filter((event) => event.type === 'event.session.archived')).toEqual([
+      { type: 'event.session.archived', payload: { sessionId: created.id } },
+    ]);
+    dispose();
+  });
+
+  it('archives a live session through the full lifecycle chain', async () => {
+    const created = await createSession();
+    const liveHandler = liveHandlerForSession(core(), created.id);
+    expect(liveHandler).toBeDefined();
+    const lifecycle = liveHandler?.accessor.get(ISessionLifecycleService);
+    const archiveSpy = vi.spyOn(lifecycle as ISessionLifecycleService, 'archive');
+    const resumeSpy = vi.spyOn(lifecycle as ISessionLifecycleService, 'resume');
+    const { events, dispose } = collectEvents();
+
+    const body = await postBatch('/api/v2/sessions:archive', { ids: [created.id] });
+    expect(body.code).toBe(0);
+    expect(body.data?.results).toEqual([{ id: created.id, ok: true }]);
+
+    // The full chain ran: archive() (no resume needed for a live session)
+    // closed and disposed the session and published the event itself.
+    expect(archiveSpy).toHaveBeenCalledWith(created.id);
+    expect(resumeSpy).not.toHaveBeenCalled();
+    expect(getLiveSessionById(core(), created.id)).toBeUndefined();
+    expect(
+      events.some(
+        (event) =>
+          event.type === 'event.session.archived' &&
+          (event.payload as { sessionId: string }).sessionId === created.id,
+      ),
+    ).toBe(true);
+    expect(await indexArchived(created.id)).toBe(true);
+    dispose();
+  });
+
+  it('reports per-item results in input order for a live/cold/missing mixed batch', async () => {
+    const live = await createSession();
+    const cold = await createSession();
+    await closeSessionById(core(), cold.id);
+
+    const body = await postBatch('/api/v2/sessions:archive', {
+      ids: [live.id, cold.id, 'sess_missing'],
+    });
+    expect(body.code).toBe(0);
+    expect(body.data?.results).toEqual([
+      { id: live.id, ok: true },
+      { id: cold.id, ok: true },
+      {
+        id: 'sess_missing',
+        ok: false,
+        error: { code: 40401, message: 'session sess_missing does not exist' },
+      },
+    ]);
+    expect(body.data?.succeeded).toBe(2);
+    expect(body.data?.failed).toBe(1);
+    expect(await indexArchived(live.id)).toBe(true);
+    expect(await indexArchived(cold.id)).toBe(true);
+  });
+
+  it('restores a cold session without materializing it and publishes no archived event', async () => {
+    const created = await createSession();
+    await closeSessionById(core(), created.id);
+    await postBatch('/api/v2/sessions:archive', { ids: [created.id] });
+    expect(await indexArchived(created.id)).toBe(true);
+
+    const handlerForSpy = vi.spyOn(core().get(IWorkspaceLifecycleService), 'handlerFor');
+    const { events, dispose } = collectEvents();
+    const before = await readStateJson(created.workspace_id, created.id);
+
+    const body = await postBatch('/api/v2/sessions:restore', { ids: [created.id] });
+    expect(body.code).toBe(0);
+    expect(body.data?.results).toEqual([{ id: created.id, ok: true }]);
+
+    expect(handlerForSpy).not.toHaveBeenCalled();
+    expect(getLiveSessionById(core(), created.id)).toBeUndefined();
+
+    const after = await readStateJson(created.workspace_id, created.id);
+    expect(after['archived']).toBe(false);
+    expect('archivedAt' in after).toBe(false);
+    expect(after['updatedAt']).toBe(before['updatedAt']);
+
+    expect(await indexArchived(created.id)).toBe(false);
+    expect(await listedIds()).toEqual([created.id]);
+    // The live restore publishes nothing either — no event at all.
+    expect(events.filter((event) => event.type === 'event.session.archived')).toEqual([]);
+    dispose();
+  });
+
+  it('restores a live session through the lifecycle chain and keeps it live', async () => {
+    const created = await createSession();
+    await postBatch('/api/v2/sessions:archive', { ids: [created.id] });
+    // Back to live-but-archived: resume materializes regardless of the flag.
+    expect(await resumeSessionById(core(), created.id)).toBeDefined();
+    const lifecycle = liveHandlerForSession(core(), created.id)?.accessor.get(
+      ISessionLifecycleService,
+    );
+    const restoreSpy = vi.spyOn(lifecycle as ISessionLifecycleService, 'restore');
+
+    const body = await postBatch('/api/v2/sessions:restore', { ids: [created.id] });
+    expect(body.code).toBe(0);
+    expect(body.data?.results).toEqual([{ id: created.id, ok: true }]);
+
+    expect(restoreSpy).toHaveBeenCalledWith(created.id);
+    expect(getLiveSessionById(core(), created.id)).toBeDefined();
+    expect(await indexArchived(created.id)).toBe(false);
+  });
+
+  it('validates the batch body: empty, missing, over the unique cap, duplicates', async () => {
+    for (const body of [{ ids: [] }, {}]) {
+      const rejected = await postBatch('/api/v2/sessions:archive', body);
+      expect(rejected.code).toBe(40001);
+      expect(rejected.data).toBeNull();
+    }
+
+    const tooMany = await postBatch('/api/v2/sessions:archive', {
+      ids: Array.from({ length: 5001 }, (_, i) => `sess_${i}`),
+    });
+    expect(tooMany.code).toBe(40001);
+
+    // Duplicates collapse before the cap; a repeated id runs once.
+    const deduped = await postBatch('/api/v2/sessions:archive', {
+      ids: Array.from({ length: 5001 }, () => 'sess_dup'),
+    });
+    expect(deduped.code).toBe(0);
+    expect(deduped.data?.results).toHaveLength(1);
+    expect(deduped.data?.results[0]?.ok).toBe(false);
+    expect(deduped.data?.results[0]?.error?.code).toBe(40401);
+  });
+});
+
 describe('mapActivityStatus', () => {
   it('maps a cold persisted failure to failed, live outcomes still win', () => {
     const coldIdle = { busy: false, mainTurnActive: false, pendingInteraction: 'none' as const, live: false as const };